CN109076466B - Transmission power of pilot signal - Google Patents

Abstract

One method comprises the steps of: in a first subset (321, 322) of a sequence of transmission intervals (302): transmitting a pilot signal (310-314) with a non-zero first transmission power according to a resource mapping (301) over a radio link (101) of a cellular network (100); in a second subset (321, 322) of the sequence of transmission intervals (302): transmitting a pilot signal (310) having a non-zero second transmission power greater than the first transmission power over the radio link (101) according to the resource mapping (301).

Description

Transmission power of pilot signal

Technical Field

Various embodiments relate to transmitting pilot signals on a radio link of a cellular network and to corresponding apparatuses.

Background

Pilot signals, sometimes also referred to as reference signals, are commonly used to determine the state of a channel implemented on a radio link of a cellular network (channel sensing). Channel sensing may include channel estimation and channel measurement. In a reference implementation, the pilot signal is transmitted repeatedly in order to take into account the time dependence of the channel state, e.g. due to time-varying multipath effects or doppler spread. The transmitted pilot signal has well-defined transmission parameters (such as amplitude and phase). From the received pilot signal and based on knowledge of the transmission parameters, characteristics of the radio link between the transmitter and the receiver can then be inferred, and conclusions drawn on the corresponding state of the channel. Examples of Uplink (UL) pilot signals are described in the third generation partnership project (3GPP) Technical Specification (TS)36.211v.13.0.0(2015-12)5.5 for the 3GPP Long Term Evolution (LTE) Radio Access Technology (RAT); an example of a Downlink (DL) pilot signal is described for 3GPP LTE RAT in 3GPP TS36.211 v.13.0.0(2015-12) 6.10.

The amplitude of the transmitted pilot signal defines the transmit power. Customizing (tailoring) transmit power may present certain challenges. In general, there is a trade-off between increased interference (for large transmit power) and channel sensing inaccuracy (for small transmit power).

Disclosure of Invention

Accordingly, there is a need for advanced techniques for transmitting pilot signals over a radio link.

According to an example, a method includes a first terminal receiving at least one uplink pilot signal on a radio link of a cellular network. The at least one uplink pilot signal is transmitted by at least one second terminal. The method also includes the first terminal sending an uplink report message over the radio link and to an access node of the cellular network. The uplink report message indicates at least one characteristic of the received at least one uplink pilot signal.

According to an example, a method comprises: the access node receives an uplink report message indicating at least one characteristic of at least one uplink pilot signal. The access node receives the uplink report message over a radio link of a cellular network and from a first terminal. The uplink pilot signal is received by the first terminal. The at least one uplink pilot signal is transmitted by at least one second terminal.

According to an example, a terminal attachable to a cellular network includes an interface. The interface is configured to transceive over a radio link of the cellular network. The terminal also includes at least one processor. The at least one processor is configured to receive at least one uplink pilot signal via the interface. The uplink pilot signal is transmitted by at least one further terminal. The at least one processor is further configured to transmit, via the interface and to an access node of the cellular network, an uplink report message. The uplink report message indicates at least one characteristic of the received at least one uplink pilot signal.

According to an example, an access node of a cellular network comprises an interface. The interface is configured to transceive over a radio link of the cellular network. The access node also includes at least one processor. The at least one processor is configured to receive, via the interface and from a first terminal, an uplink report message. The uplink report message indicates at least one characteristic of at least one uplink pilot signal received by the first terminal. The at least one uplink pilot signal is transmitted by at least one second terminal.

According to an example, a computer program product is provided. The computer program product comprises program code executable by at least one processor. Execution of the program code causes the at least one processor to perform a method. The method comprises the following steps: the first terminal receives at least one uplink pilot signal on a radio link of the cellular network. The at least one uplink pilot signal is transmitted by at least one second terminal. The method further comprises the following steps: the first terminal transmits an uplink report message over the radio link and to an access node of the cellular network. The uplink report message indicates at least one characteristic of the received at least one uplink pilot signal.

According to an example, a computer program product is provided. The computer program product comprises program code executable by at least one processor. Execution of the program code causes the at least one processor to perform a method. The method comprises the following steps: the access node receives an uplink report message indicating at least one characteristic of at least one uplink pilot signal. The access node receives the uplink report message over a radio link of a cellular network and from a first terminal. The uplink pilot signal is received by the first terminal. The at least one uplink pilot signal is transmitted by at least one second terminal.

According to an example, a method comprises: transmitting, in a first subset of a sequence of transmission intervals, a pilot signal having a non-zero first transmit power according to a resource mapping on the radio link of a cellular network. The method further comprises the following steps: transmitting, on the radio link, a pilot signal having a non-zero second transmit power in accordance with the resource mapping in a second subset of the sequence of transmission intervals. The second transmit power is greater than the first transmit power.

According to an example, an apparatus includes an interface. The interface is configured to transceive over a radio link of a cellular network. The apparatus also includes at least one processor. The at least one processor is configured to transmit, in a first subset of a sequence of transmission intervals, a pilot signal having a non-zero first transmit power according to a resource mapping on a radio link of the cellular network. The at least one processor is further configured to transmit, in a second subset of the sequence of transmission intervals, a pilot signal having a non-zero second transmit power greater than the first transmit power according to the resource mapping over the radio link.

According to an example, a computer program product is provided. The computer program product comprises program code executable by at least one processor. Execution of the program code causes the at least one processor to perform a method. The method comprises the following steps: transmitting, in a first subset of a sequence of transmission intervals, a pilot signal having a non-zero first transmit power according to a resource mapping on the radio link of a cellular network. The method further comprises the following steps: transmitting, on the radio link, a pilot signal having a non-zero second transmit power in accordance with the resource mapping in a second subset of the sequence of transmission intervals. The second transmit power is greater than the first transmit power.

According to an example, a method comprises: the first apparatus receives at least one uplink or downlink pilot signal transmitted by at least one second apparatus over a radio link of a cellular network. The method further comprises the following steps: the first apparatus transmits a report message indicating at least one characteristic of the received at least one uplink or downlink pilot signal over the radio link and to an access node of the cellular network.

According to an example, a method comprises: an access node of a cellular network receives, over a radio link of the cellular network and from a first apparatus, a report message indicating at least one characteristic of at least one uplink or downlink pilot signal received by the first apparatus, the at least one uplink or downlink pilot signal being transmitted by at least one second apparatus.

According to an example, an apparatus comprises: an interface configured to transceive over a radio link of the cellular network; at least one processor configured to receive, via the interface, at least one uplink or downlink pilot signal transmitted by at least one further apparatus, wherein the at least one processor is further configured to transmit, via the interface and to an access node of the cellular network, a report message indicating at least one characteristic of the received at least one uplink or downlink pilot signal.

According to an example, an access node of a cellular network comprises: an interface configured to transceive over a radio link of the cellular network; at least one processor configured to receive, via the interface and from a first apparatus, a report message indicating at least one characteristic of at least one uplink or downlink pilot signal received by the first apparatus, the at least one uplink or downlink pilot signal transmitted by at least one second apparatus.

It is to be understood that the features mentioned above and those yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Drawings

Fig. 1 is a schematic diagram of a cellular network in accordance with various embodiments.

Fig. 2 is a schematic diagram of channels implemented on a radio link of a cellular network, in accordance with various embodiments.

Fig. 3 is a schematic diagram of a repetition resource mapping for pilot signals transmitted in a sequence of transmission intervals, according to various embodiments, wherein the repetition resource mapping according to the embodiments of fig. 3 employs frequency division multiple access in order to mitigate interference between multiple terminals transmitting pilot signals.

Fig. 4 is a schematic diagram of a repetition resource mapping for pilot signals transmitted in subsequent transmission intervals, according to various embodiments, wherein the repetition resource mapping according to the embodiments of fig. 4 employs time division multiple access in order to mitigate interference between multiple terminals transmitting pilot signals.

Fig. 5 is a schematic diagram of repetition of a repetition resource mapping for pilot signals, in accordance with various embodiments.

Fig. 6 is a schematic diagram of repetition of a repetition resource mapping for pilot signals, in accordance with various embodiments.

Fig. 7 schematically illustrates a first terminal receiving an uplink pilot signal transmitted by a second terminal, in accordance with various embodiments.

Fig. 8A is a signaling diagram illustrating a first terminal receiving an uplink pilot signal transmitted by a second terminal and also illustrating the first terminal transmitting an uplink report message indicating characteristics of the received uplink pilot signal, in accordance with various embodiments.

Fig. 8B is a signaling diagram illustrating a first terminal receiving an uplink pilot signal transmitted by a second terminal and also illustrating the first terminal transmitting an uplink report message indicating characteristics of the received uplink pilot signal, in accordance with various embodiments.

Fig. 9A is a signaling diagram illustrating a first terminal receiving a plurality of uplink pilot signals transmitted by a second terminal and also illustrating the first terminal transmitting an uplink report message indicating characteristics of the received plurality of uplink pilot signals, in accordance with various embodiments.

Fig. 9B is a signaling diagram illustrating a first terminal receiving a plurality of uplink pilot signals transmitted by a second terminal and also illustrating the first terminal transmitting an uplink report message indicating characteristics of the received plurality of uplink pilot signals, in accordance with various embodiments.

Fig. 10A is a signaling diagram illustrating a first terminal receiving multiple uplink pilot signals transmitted by a second terminal and also illustrating the first terminal transmitting an uplink report message indicating characteristics of the received multiple uplink pilot signals, wherein, in the scenario of fig. 10A, the first terminal receives the uplink pilot signals during a silence period (silence period), in accordance with various embodiments.

Fig. 10B is a signaling diagram illustrating a first terminal receiving a plurality of uplink pilot signals transmitted by a plurality of second terminals and also illustrating the first terminal transmitting an uplink report message indicating characteristics of the received plurality of uplink pilot signals, in accordance with various embodiments.

Fig. 11A is a signaling diagram illustrating a first terminal receiving an uplink pilot signal transmitted by a second terminal, the first terminal transmitting an uplink report message indicating characteristics of the received uplink pilot signal, and further illustrating occasionally scheduling (schedule) of respective transmission intervals including the uplink pilot signal, in accordance with various embodiments.

Fig. 11B is a signaling diagram illustrating a first terminal receiving an uplink pilot signal transmitted by a second terminal, the first terminal transmitting an uplink report message indicating characteristics of the received uplink pilot signal, and further illustrating persistently scheduling a respective transmission interval including the uplink pilot signal, in accordance with various embodiments.

Fig. 12 schematically illustrates transmitting a power-boosted pilot signal in accordance with various embodiments.

Fig. 13A schematically illustrates transmitting pilot signals having a first transmit power in a first subset of a sequence of transmission intervals and transmitting pilot signals having a second transmit power greater than the first transmit power in a second subset of the sequence of transmission intervals, in accordance with various embodiments.

Fig. 13B schematically illustrates a first transmit power and a second transmit power, and further illustrates a factor by which the second transmit power is greater than the first transmit power, in accordance with various embodiments.

Fig. 14 schematically illustrates a time dependence of the second transmission power by a factor greater than the first transmission power, in accordance with various embodiments.

Fig. 15 schematically illustrates a time dependence of the second transmit power by a factor greater than the first transmit power, in accordance with various embodiments.

Fig. 16 schematically illustrates a time dependence of the second transmit power by a factor greater than the first transmit power, in accordance with various embodiments.

Fig. 17 schematically illustrates a handover (handoff) scenario in which an uplink pilot signal with increased power is considered for handoff, in accordance with various embodiments.

Fig. 18 schematically illustrates a handover scenario in which a power boosted uplink pilot signal is considered for handover, in accordance with various embodiments.

Fig. 19 schematically illustrates a handover scenario in which a power boosted uplink pilot signal is considered for handover, in accordance with various embodiments.

Fig. 20 is a signaling diagram illustrating persistently scheduling a transmission interval including a second subset of pilot signals having a second transmit power, in accordance with various embodiments.

Fig. 21 is a signaling diagram illustrating sporadically scheduling a transmission interval including a second subset of pilot signals having a second transmit power in accordance with various embodiments.

Fig. 22 is a signaling diagram illustrating transmission of a pilot signal in a second subset of transmission intervals and having a second transmit power, wherein the pilot signal indicates the second transmit power, in accordance with various embodiments.

Fig. 23 is a signaling diagram illustrating transmitting a pilot signal in a second subset of transmission intervals and having a second transmit power, and further illustrating transmitting a control message indicating the second transmit power, in accordance with various embodiments.

Fig. 24 is a signaling diagram illustrating a handover scenario in accordance with various embodiments.

Fig. 25 is a signaling diagram illustrating scheduling of transmission intervals between two access nodes of a cellular network including a second subset of pilot signals having a second transmit power greater than a first transmit power, in accordance with various embodiments.

Fig. 26 schematically illustrates a terminal according to various embodiments.

Fig. 27 schematically illustrates an access node in accordance with various embodiments.

FIG. 28 schematically illustrates a method in accordance with various embodiments.

FIG. 29 schematically illustrates a method in accordance with various embodiments.

FIG. 30 schematically illustrates a method according to various embodiments.

FIG. 31 schematically illustrates a method in accordance with various embodiments.

FIG. 32 schematically illustrates a method in accordance with various embodiments.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following description of the embodiments is not to be taken in a limiting sense. The scope of the present invention is not intended to be limited by the embodiments described below or the accompanying drawings, which are to be considered only as illustrative.

The figures are to be regarded as schematic representations and the elements illustrated in the figures are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose are apparent to those skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the figures or described herein may also be achieved through an indirect connection or coupling. The coupling between the components may also be established by a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

Techniques for transmitting pilot signals over radio links of a cellular network are described below. The techniques may be applied to an Uplink (UL) pilot signal transmitted from a terminal to an access node. Alternatively or additionally, the techniques may be applied to Downlink (DL) pilot signals transmitted from an access node to a terminal. Alternatively or additionally, the techniques may also be applied to pilot signals (i.e., sidelink pilot signals or relay pilot signals) transmitted between two terminals for device-to-device (D2D) communication.

In the following, techniques are described that enable flexible customization (tailor) of the transmit and/or receive (transmit) pilot signals. Customization may involve flexibly setting certain transmission characteristics (such as amplitude) of the pilot signal. The customization may involve the first apparatus flexibly receiving pilot signals intended for a different second apparatus and transmitted by a third apparatus.

In some examples, the techniques involve dynamically adjusting transmit power of pilot signals. In some examples, the transmit power of the pilot signal may be adjusted between two levels, three levels, or more over time. In some examples, the transmit power of the pilot signal is temporarily and sporadically increased to a second transmit power that is higher than the baseline first transmit power.

By dynamically adjusting the transmit power, a greater number of devices may be enabled to receive the increased power pilot signal. Thus, a greater number of apparatuses, such as further access nodes and/or terminals, may benefit from the information obtainable from the received pilot signals. For example, channel sensing may be achieved with high accuracy because more information is available.

In some examples, the techniques involve a first terminal receiving at least one uplink pilot signal transmitted by at least one second terminal. The at least one uplink pilot signal may be directed/intended to an access node of the cellular network. Accordingly, the first terminal may intercept the transmission and receive the at least one uplink pilot signal.

Additional information regarding the status of the channel implemented on the radio link may be collected by the first terminal receiving the uplink pilot signal. The positioning of the first terminal may also be performed with respect to at least one of the at least one second terminal and/or the access node.

In some examples, techniques are provided that enable reducing/mitigating interference between multiple apparatuses transmitting pilot signals. In some examples, interference is mitigated by orthogonally transmitting pilot signals between the plurality of apparatuses. Orthogonality may be achieved by utilizing Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and/or Frequency Division Multiple Access (FDMA). In some examples, inter-cell interference is mitigated by scheduling pilot signals across multiple cells. In some examples, intra-cell and/or inter-cell interference is mitigated by appropriately setting the transmit power of the pilot signals.

The techniques described herein may be applied to various use cases, including evolution of existing LTE systems and next generation cellular networks (e.g., New Radio (NR) access technologies for 5G cellular networks). A particular use case is a multiple-input multiple-output (MIMO) scenario, such as a massive MIMO (mami) scenario. The initial phase of MAMI has just been developed in 3GPP as part of LTE evolution and is referred to as full-dimensional (FD) -MIMO. See 3GPP TS 36.897. MAMI is typically deployed by using massive base station antennas and few terminal antennas, the main objective being to achieve higher order multi-user MIMO. MAMI provides high spatial diversity. MIMO systems may use multiple transmit antennas and/or multiple receive antennas for communication over a radio link at an access node. MIMO enables coding techniques that use both the temporal and spatial dimensions to transmit information. The coding provided in MIMO systems allows considerable spectral and energy efficiency. MAMI base stations typically include a relatively large number of antennas, e.g., tens or even over a hundred antennas with associated receiver circuitry. The additional antenna of the MAMI device allows for spatial focusing of radio energy during transmission; and direction sensitive reception. This technique improves spectral efficiency and radiant energy efficiency. MAMI scenarios may benefit from highly accurate channel sensing, which is made possible by the techniques described herein.

Fig. 1 illustrates an architecture of a cellular network 100 according to some example implementations. In particular, the cellular network 100 according to the example of fig. 1 implements a 3GPP LTE architecture, sometimes referred to as Evolved Packet System (EPS). However, this is for exemplary purposes only. In particular, for illustrative purposes only, various scenarios will be explained in the context of a radio link 101 between terminals 130-1, 130-2 and a cellular network 100 operating according to the 3GPP LTE architecture. Similar techniques can be readily applied to various 3GPP specified architectures such as global system for mobile communications (GSM), Wideband Code Division Multiple Access (WCDMA), General Packet Radio Service (GPRS), enhanced data rates for GSM evolution (EDGE), enhanced GPRS (egprs), Universal Mobile Telecommunications System (UMTS), and corresponding architectures for High Speed Packet Access (HSPA) and associated cellular networks.

Two terminals 130-1, 130-2 are connected to an access node 112 of the cellular network 100 via a radio link 101. The two terminals 130-1, 130-2 may also be connected to each other via a radio link 101 (D2D communication or sidelink communication). Access node 112 and terminals 130-1, 130-2 implement evolved UMTS terrestrial radio access technology (E-UTRAN); thus, the access point node 112 is an eNB 112.

For example, the terminals 130-1, 130-2 may be selected from the group consisting of: a smart phone; a cellular telephone; a tablet computer; a notebook computer; a computer; a smart TV; machine Type Communication (MTC) devices, internet of things devices; and the like.

Communication over the radio link 101 may be in the UL and/or DL direction, or D2D. Details of the radio link 101 are illustrated in fig. 2. The radio link 101 implements multiple channels 261 and 263. Radio resources 305 are associated with each channel 261-. Each channel 261- "263 includes a plurality of resources 305 defined in the time domain and the frequency domain. The resources 305 are typically made up of appropriate transmission intervals, for example, in the case of LTE RAT entry slots, subframes, frames, and radio frames (none shown in fig. 2).

For example, resources 305 may correspond to individual symbols such as Orthogonal Frequency Division Multiplexing (OFDM) symbols in 3GPP LTE RAT. For example, resource 305 may correspond to a single resource element or multiple resource elements, sometimes referred to as resource blocks. A resource block includes a plurality of subcarriers. Thus, the resources may have different bandwidths (e.g., 15kHz or 180kHz) depending on the particular implementation.

The control channels 261, 262 may be associated with control messages. The control messages may configure the operation of the terminals 130-1, 130-2, the eNB112, and/or the radio link 101. For example, Radio Resource Control (RRC) messages and/or HARQ ACKs and NACKs may be exchanged via a control channel. The control channels 261, 262 may thus correspond to a Physical Downlink Control Channel (PDCCH) and/or a Physical Uplink Control Channel (PUCCH) and/or a physical hybrid ARQ indicator channel (PHICH) in accordance with the E-UTRAN RAT.

In addition, the shared channel 263 is associated with payload messages carrying higher layer user plane data packets associated with a given service implemented by the terminals 130-1, 130-2 and the eNB 112. The shared channel 263 may be a Physical Downlink Shared Channel (PDSCH) or a Physical Uplink Shared Channel (PUSCH) according to the E-UTRAN RAT. Shared channel 263 may also sometimes be used for sidelink communications.

A relay channel may also be implemented. The relay channel allows data to be communicated between the first terminals 130-1, 130-2 and the eNB112 via an intermediate relay. The intermediate relay may be implemented by the second terminals 130-1, 130-2. See, for example, 3GPP Technical Report (TR)36.806v.9.0.0 (2010-03).

The various channels 261-263 may be implemented using MIMO or MAMI techniques (MIMO channels). Here, spatial diversity is obtained by using multiple transmit and/or receive antennas.

Some resources 305 are used to transmit pilot signals 310. The pilot signal 310 enables channel sensing. The pilot signals 310 may be uplink pilot signals, downlink pilot signals, and/or sidelink pilot signals. The pilot signals 310 may be cell-specific and/or terminal-specific. The pilot signal 310 may have well-defined transmission characteristics. Based on the comparison of the reception characteristics with the transmission characteristics, conclusions can be drawn about the channel state. Each pilot signal may include one or more symbols (e.g., OFDM symbols). The symbols of the pilot signal may be generated by a sequence generator. Different pilot signals transmitted in the same resource 305 may be orthogonally coded with respect to each other by CDMA techniques; this can be achieved by properly designing the sequencer. A sequence of subsequently transmitted pilot signals 310 may be generated based on a sequence generator. The sequence generator may map, for example, the particular resource 305 transmitting the respective pilot signal to the real and imaginary parts of the respective OFDM symbol. Thus, the particular symbol value of pilot signal 310 may vary in different instances depending on the sequence generator.

Turning again to fig. 1, the eNB112 is connected with a gateway node implemented by a Serving Gateway (SGW) 117. The SGW 117 may route and forward payload data and may act as a mobility anchor during handover of the terminals 130-1, 130-2 between neighboring cells.

The SGW 117 is connected to a gateway node implemented by a packet data network gateway (PGW) 118. PGW 118 serves as an exit and entry point to cellular network 110 for data towards packet data network 121 (PDN): for this purpose, the PGW 118 is connected to the PDN 121. There may be more than one PDN 121. Each PDN 121 is uniquely identified by an access node name (APN). The terminals 130-1, 130-2 use the APN to seek access to a certain PDN 121 (e.g. the internet).

PGW 118 may be an end point (dashed line in fig. 1) of an end-to-end connection 160 for packetized payload data for terminal 130-1. The end-to-end connection 160 may be used to transfer data for a particular service. Different services may use different end-to-end connections 160 or may at least partly share a certain end-to-end connection. The end-to-end connection 160 may be implemented by one or more bearers (bearer) used for transporting service specific data. The EPS bearer is characterized by a specific set of quality of service parameters indicated by a QoS Class Identifier (QCI).

Fig. 3 illustrates aspects relating to allocating resources 305 for transmitting pilot signals 311-318. In particular, fig. 3 illustrates aspects related to repeating resource maps 301, 301A. Although reference is primarily made hereinafter to duplicate resource mappings, in other examples, non-duplicate resource mappings may also be employed. The resource map 301, 301A defines the occupancy of resources 305 for a particular type of pilot signal for a particular terminal 130-1, 130-2. The different resource maps 301, 301A may avoid interference by FDMA, TDMA, and/or CDMA techniques.

In fig. 3, an excerpt of a repeating resource map 301, 301A for a given transmission interval 302 is illustrated; for example, the transmission interval 302 may be a radio frame, block, subframe, or slot. Repetition of the duplicate resource map 301, 301A may be implemented for subsequent time intervals.

In the example of fig. 3, first pilot signals 311-314 and second pilot signals 315-318 are illustrated. Transmitting the first pilot signal 311-314 (the fully black portion in FIG. 3) according to the repetitive resource mapping 301 between the terminal 130-1 and the eNB 112; the second pilot signal 315 is transmitted 318 based on the repeated resource mapping 301A between the terminal 130-2 and the eNB 112. For example, the first pilot signal 311-314 may be a UL pilot signal transmitted by the terminal 130-1 and received by the eNB 112; the first pilot signal 311-314 may also be a DL pilot signal transmitted by the eNB112 and received by the terminal 130-1. Similar considerations apply to the second pilot signal 315-318 with respect to terminal 130-2.

Each type of pilot signal may have an associated unique repetition resource map 301, 301A. That is, different repetition resource mappings 301, 301A may distinguish different types of pilot signals from each other. Different terminals 130-1, 130-2 may also employ different repetition resource mappings 301, 301A; this may allow the eNB112 to distinguish the identity of the originator of the received UL pilot signal.

In fig. 3, a silence period 307 of terminal 130-1 is illustrated; terminal 130-1 does not transmit during silence period 307. By implementing such silence periods 307, interference may be mitigated relative to additional terminals (not shown in fig. 3) that require protected resources for transmitting, e.g., pilot signals.

As can be seen from fig. 3, in order to avoid interference between transmitting the first pilot signal 311-314 and transmitting the second pilot signal 315-318, FDMA techniques are employed with respect to the repetitive resource mapping 301, 301A.

Fig. 4 illustrates aspects relating to allocating resources 305 for transmitting pilot signals 311-318. Fig. 4 generally corresponds to fig. 3. However, in the case of fig. 4, instead of employing FDMA techniques to transmit the first pilot signal 311-.

As can be seen from fig. 4, terminal 130-2 transmits pilot signals 315-318 during silence period 307 of terminal 130-1. Thus, the terminal 130-1 is able to receive the second pilot signal 315 transmitted by the terminal 130-2 as well as 318. Generally, in the scenario of FIG. 3, the terminal 130-1 may also receive the second pilot signal 315 transmitted by the terminal 130-2; this situation may be facilitated by the duplex communication capabilities of terminal 130-1, for example.

The repetition resource mapping 301, 301A may be specified by control signaling. For example, a plurality of candidate resource mappings may be predefined. For example, based on the control signaling, a particular resource mapping may be selected that is applicable for transmitting the pilot signals 311, 314, 315, 318. For example, the physical cell identity may be associated with a specific resource mapping, see 3GPP TS36.211V13.1.0, 2016, section 6.10.1.

The resource maps 301, 301A of fig. 3 and 4 may be repeatedly applied. The periodicity of the repetition may correspond to the transmission interval 302 or multiple transmission intervals 302.

Next, the pilot signal is referred to the signaling diagrams of fig. 8A, 8B, 9A, 9B, 10A, 10B, 11A, 11B, and 20 to 25. These pilot signals may be configured in accordance with the pilot signals 310-318 as discussed with reference to fig. 3 and 4.

Fig. 5 illustrates aspects related to the repetition of the repetition resource map 301. In fig. 5, a mapping of a repetition resource mapping 301 to a subsequent transmission interval 302 is illustrated. In the example of fig. 5, the repetition resource map 301 is repeated for each transmission interval 302; thus, the period 303 of the repeated resource mapping 301 corresponds to the duration of the transmission interval 302.

Fig. 6 illustrates aspects related to the repetition of the repetition resource map 301. In fig. 6, a mapping of a repetition resource mapping 301 to a subsequent transmission interval 302 is illustrated. In the example of fig. 6, the repetition resource map 301 is repeated every other transmission interval 302; thus, the period 303 of the repetition resource map 301 corresponds to twice the duration of the transmission interval 302. In other examples, even longer periods are contemplated. Different repetition resource mappings may have different periodicity.

Fig. 7 illustrates aspects related to terminal 130-1 receiving the UL pilot signal transmitted by terminals 130-2, 130-3. In fig. 7, terminal 130-1 is located between terminals 130-2, 130-3. Terminals 130-2, 130-3 transmit UL pilot signals. The UL pilot signals are intended for the eNB 112. Accordingly, the transmit power of the UL pilot signal transmitted by the terminals 130-2, 130-3, 130-4 is set so that the eNB112 defining the cell 112A can receive the UL pilot signal. The eNB112 may implement channel sensing according to a reference technology based on the received UL pilot signals.

The Ul pilot signals are intended for the eNB112 by transmitting them according to a specific repetition resource mapping and/or generating a pilot signal sequence according to a specific sequence generator, which is pre-negotiated between the eNB and the transmitting terminals 130-2, 130-3. Because the UL pilot signal is intended for the eNB112, the eNB112 is configured to determine at least one characteristic of the UL pilot signal and estimate the state of the channel 261 and 263 based on the determined at least one characteristic. Accordingly, the eNB112 may perform channel sensing based on the received UL pilot signals.

The UL pilot signal is associated with a particular transmit power. The transmit power defines the coverage areas 130-2A, 130-3A (illustrated by dashed lines in fig. 7) in which pilot signals may be received. As can be seen from fig. 7, terminal 130-1 may receive the UL pilot signals transmitted by terminals 130-2, 130-3. Terminal 130-1 may not be able to receive the UL pilot signal transmitted by terminal 130-4.

Fig. 8A illustrates aspects related to terminal 130-1 receiving UL pilot signal 901 transmitted by terminal 130-2. Fig. 8A is a signaling diagram illustrating communications between eNB112 and terminals 130-1 and 130-2.

Terminal 130-2 transmits UL pilot signal 901. The UL pilot signal 901 may be intended for the eNB 112. For example, UL pilot signal 901 may be cell-specific for cell 112A and/or may be terminal-specific for terminal 130-2. The eNB112 receives the UL pilot signal 901. The eNB112 performs channel sensing based on the received UL pilot signal 901.

Transmission of UL pilot signal 901 is intercepted by terminal 130-1. Terminal 130-1 receives UL pilot signal 901 transmitted by terminal 130-2. The terminal 130-1 then transmits a UL report message 902 over the radio link 101 to the eNB112, the UL report message 902 indicating characteristics of the received UL pilot signal 901. The eNB112 receives an UL report message 902 over the radio link 101 and from the terminal 130-1, the UL report message 902 indicating characteristics of an UL pilot signal 901 received by the terminal 130-1 and transmitted by the terminal 130-2.

The UL report message 902 may enable the eNB112 to collect additional information about the status of the radio link 101 in the area of the terminal 130-1. Based on this, channel sensing performed by the eNB112 may be performed with higher accuracy. Remote channel sensing may be performed.

For example, UL report message 902 may indicate one or more characteristics selected from the group consisting of: the amplitude of the received UL pilot signal 901; the phase of the received UL pilot signal 901; resource 305 transmitting received UL pilot signal 901; a time offset of received UL pilot signal 305, e.g., relative to a synchronization clock of eNB112 and terminals 130-1, 130-2; and the angle of arrival of the received UL pilot signal 901. Such a characteristic allows accurate channel sensing. Remote channel sensing may be performed.

Fig. 8B illustrates aspects related to terminal 130-1 receiving UL pilot signal 901 transmitted by terminal 130-2. FIG. 8B generally corresponds to FIG. 8A; however, in the example of fig. 8B, the UL pilot signal 901 is received only by the terminal 130-1, and not by the eNB 112. This scenario may apply to the case where terminal 130-1 is attached to cellular network 100 via eNB112, but terminal 130-2 is attached to the cellular network via a further access node (not illustrated in fig. 8B). The further access node may receive a pilot signal 901 and may perform channel sensing based on the received pilot signal 901. Thus, in various examples described herein, it is not germane that UL report message 902 is intended for the same access node as the at least one UL pilot signal 901.

In the example of fig. 8A, 8B, the UL report message 902 indicates at least one characteristic of a single UL pilot signal 901. In other examples, information about multiple UL pilot signals may be aggregated into a single UL report message. Thereby, signaling overhead is reduced and traffic on the radio link 101 is reduced.

FIG. 9A illustrates aspects related to terminal 130-1 receiving the multiple UL pilot signals 911-913 transmitted by terminal 130-2. Fig. 9A generally corresponds to the example of fig. 8A, however, in the example of fig. 9A, information regarding multiple UL pilot signals 911-.

While in the example of FIG. 9A all UL pilot signals 911-913 originate from the same terminal 130-2, in other examples terminal 130-1 may receive multiple pilot signals originating from multiple terminals. Information on multiple pilot signals originating from multiple terminals may also be aggregated into a single UL report message 902. In a scenario, channel sensing may thus be facilitated by including an indicator in UL report message 902 indicating the identity of the originator of the received UL pilot signal. The indicator may indicate the identity explicitly or implicitly, e.g. via a specific repetition resource map 301, 301A.

In various examples, UL report message 902 may include at least one characteristic parsed for each of UL pilot signals 911-. In other examples, UL report message 902 may also include an average or otherwise obtained value determined based on a combination of the received plurality of UL pilot signals 911-. For example, certain characteristics such as the amplitude and/or phase of received UL pilot signal 911-. Thereby, signaling overhead and traffic on the radio link 101 is reduced.

FIG. 9B illustrates aspects related to terminal 130-1 receiving the multiple UL pilot signals 911-913 transmitted by terminal 130-2. Fig. 9B generally corresponds to the example of fig. 9A, however, in the example of fig. 9B, terminal 130-1 does not receive UL pilot signal 911.

A first reason for terminal 130-1 not receiving UL pilot signal 911 may be that terminal 130-2 transmits UL pilot signal 911 at a lower transmit power if compared to UL pilot signals 912, 913. For example, terminal 130-2 may be configured to temporarily increase the transmit power of UL pilot signals 912, 913 in order to facilitate its reception by terminal 130-1. Thus, terminal 130-1 may be out of range with respect to UL pilot signal 911 transmitted at a lower transmit power; and terminal 130-1 may be within range 130-2A relative to UL pilot signals 912, 913.

A second reason for terminal 130-1 not receiving UL pilot signal 911 may be that terminal 130-1 has moved into range 130-2A of UL pilot signal transmission by terminal 130-2 between transmitting UL pilot signals 911, 912.

In the scenario according to fig. 9B, channel sensing may thus be facilitated by including resource identification information of received UL pilot signals 912, 913 in UL report message 902. The resource identification information may include resource location information and/or timestamp information.

Fig. 10A illustrates aspects related to terminal 130-1 receiving multiple UL pilot signals 921, 923 transmitted by terminal 130-2. Fig. 10A generally corresponds to the example of fig. 9A; however, in the example of FIG. 10A, terminal 130-1 does not receive pilot signal 922. This is because UL pilot signal 922 is not transmitted during silence period 307. In the example of fig. 10A, terminal 130-1 is only able to receive pilot signals during silence period 307. This may be because the terminal 130-1 is restricted in hardware operation.

Thus, in general, terminal 130-1 is not forced to receive all of the UL pilot signal sequences transmitted by terminal 130-2 in this sequence of transmission intervals 302 in accordance with the various examples described herein; conversely, it is sufficient if terminal 130-1 receives the UL pilot signal in a subset of the sequence of transmission intervals 302. For example, the transmission interval 302 of the subset may be scheduled between the terminal 130-1 and the eNB 112-the terminal 130-1 receives the UL pilot signal in the transmission interval.

Fig. 10B illustrates aspects related to terminal 130-1 receiving UL pilot signals 927, 928 transmitted by terminals 130-2, 130-3. Fig. 10B generally corresponds to fig. 8A and 8B; however, terminal 130-1 receives and aggregates information about the UL pilot signals 927, 928 transmitted by both terminals 130-2, 130-3. The UL pilot signals 927, 928 may or may not be intended for the same eNB112 and may or may not be received by the eNB 112. The report message 929 indicates the characteristics of the two pilot signals 927, 928.

Fig. 11A illustrates aspects related to terminal 130-1 receiving the UL pilot signal. Fig. 11A also illustrates aspects of sporadically scheduling transmission intervals 302 of subsets between eNB112 and terminal 130-1. Scheduling control message 931 is transmitted by eNB112 and received by terminal 130-1. Scheduling control message 931 indicates resource identification information/timing of a UL pilot signal 932 that is subsequently transmitted by terminal 130-2. Scheduling control message 931 prompts terminal 130-1 to receive UL pilot signal 932. Terminal 130-1 receives UL pilot signal 932 in response to receiving scheduling control message 931.

By employing such sporadic scheduling, terminal 130-1 removes the need to blindly enable the receiver circuitry, i.e., does not need to know the timing of the UL pilot signal transmitted by terminal 130-2. The energy consumption can be reduced.

Fig. 11B illustrates aspects related to terminal 130-1 receiving multiple UL pilot signals 942, 944. Fig. 11B also illustrates aspects of persistently scheduling the transmission intervals 302 of the subset between the eNB112 and the terminal 130-1. In the example of fig. 11B, the scheduling control message 931 specifies a reproduction time point at which the terminal 130-1 continuously receives the UL pilot signals 942, 944 transmitted by the terminal 130-2. Such a reproduction time point may be defined with respect to a certain period 931A, for example.

As can be seen from fig. 11B, UL pilot signals 942, 944 are part of the transmission intervals 302 of the corresponding subset; terminal 130-1, on the other hand, does not receive UL pilot signal 943 because the corresponding transmission interval 302 is not part of the subset. The report message 902 includes characteristics of the received UL pilot signals 942, 944.

This situation of scheduling the transmission interval 302 of the subset between the terminal 130-1 and the eNB112 according to the examples of fig. 11A, 11B may be particularly useful in case the terminal 130-2 temporarily increases the transmit power of the UL pilot signal from time to time. Terminal 130-1 may then be assured that the receiver circuitry of the interface is enabled to receive the power-boosted UL pilot signal. Similar considerations apply when the eNB112 transmits power-boosted DL pilot signals from time to time.

Fig. 12 illustrates aspects related to increasing the transmit power of the UL pilot signal. Fig. 12 generally corresponds to fig. 7. However, from a comparison of fig. 7 and fig. 12, it is apparent that the range 130-4A of the UL pilot signal transmitted by terminal 130-4 increases for the scenario of fig. 12. This is because the terminal 130-4 transmits the UL pilot signal at a higher transmission power for the case of fig. 12. In order to avoid an increase in interference due to power up transmission of the UL pilot signal, the transmit power may be temporarily increased in a limited time.

Such a temporary increase of the transmission power can be conceived not only for the UL pilot signals in the above-described case, but generally for all types of UL pilot signals including UL pilot signals, DL pilot signals, sidelink pilot signals, cell-specific pilot signals, and terminal-specific pilot signals. The additional node or device may then receive the increased power pilot signal; the power-boosted pilot signal may have a beacon function.

FIG. 13A illustrates aspects related to transmitting pilot signals 311 and 314 at a non-zero first transmit power in a first subset 321 of transmission intervals 302; and aspects of transmitting UL pilot signal 311-. By employing both the first and second transmit powers, the trade-off between interference (due to the larger second transmit power) and channel sensing inaccuracy (due to fewer nodes receiving pilot signals with lower first transmit powers) may be optimized. Increased coverage compromises for increased interference.

In the example of fig. 13A, the transmission power of the same type of pilot signals 311 and 314 is thus temporarily adjusted. A temporary transmit power boost is performed for a given type of pilot signal 311-314. The pilot signals 311 and 314 are all of the same type because the same repetition resource mapping 301 is used. The various pilot signals 311-314 transmitted at the first and second transmit powers also belong to the same sequence, sometimes referred to as a generator code, associated with a single sequence generator. For example, an example of a sequencer is given by 3GPP TS36.211v13.0.0 (2015-12); for CRS, for example, the sequence generation is specified by section 6.10.1.1; for SRS, for example, the sequence generation is specified in section 5.5.3.1.

From fig. 13A, it is apparent that the transmission intervals 302 of the second subset 322 are arranged between the transmission intervals 302 of the first subset 321. In the example of fig. 13A, the first and second subsets 331, 322 are interleaved in the time domain. Thus, the first subset 331 and the second subset 332 are alternately active for an arbitrary period of time. Such interleaving in the time domain may be applicable to the various examples discussed herein.

In general, the first and second subsets 331, 332 may be at least partially different from each other, e.g., with respect to at least one of: time domain, frequency domain, code domain, and/or spatial domain. Alternatively or additionally, different duplexing techniques and/or interleaving techniques may be combined with respect to each other. Generally, the first and second subsets 331, 332 may be distinguished from each other in some way. For example, the first subset 331 and the second subset 3 may be distinguished from each other using a temporal, frequency, or spatial approach, or a combination thereof. Code division is also possible.

From fig. 13A, it is apparent that the transmission intervals 302 of the second subset 322, for example, recur with a period 322A. To avoid excessive interference due to the large number of power-boosted pilot signals 311-314, it may be desirable to limit the number of transmission intervals 302 of the second subset 302. For example, the size of the transmission intervals 302 included in the first subset 321 (i.e., the number of transmission intervals 302) may be at least 2 times, preferably at least 100 times, more preferably at least 1000 times the size of the second subset 322 (in the example of fig. 13A, the size of the first subset 321 is 3 times the size of the second subset 322).

Not closely related, all pilot signals 311 and 314 within the transmission interval 302 of the second subset 321 are transmitted at the second transmit power. Generally, it is sufficient if a single or a part of all pilot signals 311- < - > 314 within a given transmission interval 302 of the second subset 321 are transmitted with the second transmission power, while the remaining pilot signals 311- < - > 314 are transmitted with the first transmission power. In some examples, however, all pilot signals 311 and 314 within the transmission interval 302 of the second subset 321 may be transmitted at the second transmit power.

Fig. 13B illustrates aspects relating to first and second transmit powers 231, 232 associated with first and second subsets 321, 322, respectively. From fig. 13B, it is apparent that the second transmission power 232 is larger than the first transmission power 231 by a factor 233. For example, the factor may correspond to at least 1dB, preferably at least 3dB, more preferably at least 10 dB. For example, the second transmit power 232 may be determined to be equal to a maximum transmit power supported by a corresponding interface or analog transmitter stage of the transmitting device. Beyond this, additional or other considerations may be considered in determining the factor 233; examples include: and at least partially randomized and/or optimized. For example, the optimization may be performed for an element selected from the group consisting of: interference; the accuracy of the channel sensing; a tradeoff between interference and coverage; and the like. In addition to such examples, additional or other considerations may be considered in determining the factor 233. Examples include: the location of the terminal transmitting the pilot signal; and handover of terminals transmitting pilot signals.

Fig. 14 illustrates aspects related to determining a factor 233 between the second transmit power 232 and the first transmit power 231. In the example of fig. 14, factor 233 is constant over time at a finite (i.e., non-zero) value.

Fig. 15 illustrates aspects related to determining a factor 233 between the second transmit power 232 and the first transmit power 231. In the example of fig. 15, factor 233 changes over time. This may be due to, for example, the determination of factor 233; mobility/time-varying location of the terminal transmitting the pilot signal; and a random contribution of a handover of the terminal that occurs at a certain point in time. Thus, the time dependence of the factor 233 may depend on the context.

Fig. 16 illustrates aspects related to determining a factor 233 between the second transmit power 232 and the first transmit power 231. In the example of fig. 16, factor 233 changes over time. Specifically, factor 233 varies between zero dB and a finite value. As can be seen, in various examples, the power boosting of the pilot signal can be selectively performed according to certain triggering criteria and/or background dependencies. That is, transmitting the pilot signal having the second transmit power may be selectively performed according to certain triggering criteria and/or background dependencies.

Although the above aspects have been explained above for the time dependency and determination of the factor 233 between the second transmission power 232 and the first transmission power 231, similar considerations may easily be applied to the time dependency and determination of the factor between the size of the second subset 232 and the size of the first subset 231.

Fig. 17 illustrates aspects related to a handover scenario. Fig. 17 illustrates aspects for the case where terminal 130-1 transmits the UL pilot signal. The terminal 130-1 attaches to the cellular network via the eNB 112-1. In FIG. 17, the terminal 130-1 is located near the edge of the cell 112-1A of the eNB 112-1. A first range 130-1A (dotted and dashed line in fig. 17) associated with a first transmit power 231 is illustrated; further, a second range 130-1B (dashed line in FIG. 17) associated with a second transmit power 232 is illustrated. It is apparent that only pilot signals having the second transmit power 232 may be received by both enB112-1 and the eNB112-2 associated with cell 112-2A (eNB 112-3 may not be able to receive any UL pilot signals transmitted by terminal 130-1). Thus, channel sensing by the eNB112-2 may be facilitated by using the pilot signal with the second transmit power 232. Further, by employing the second transmit power 232 for the UL pilot signal in the transmission interval 302 of the second subset 322, the eNB112-2 may be informed in advance that the terminal 130-1 is close to the cell 112-2A. This information may be used to reliably perform a handover from eNB112-1 to eNB 112-2.

In some examples, if terminal 130-1 is near an edge of cell 112-1A, power boosting may be selectively performed (i.e., transmitting a pilot signal with second transmit power 232); that is, the location of the terminal 130-1 may be considered in determining the factor 233 between the second transmit power 232 and the first transmit power 231 (see fig. 16).

In some examples, it may be desirable to schedule the transmission intervals 302 of the second subset 322 between the eNB112-1 and the eNB 112-2. This may be done in order to mitigate inter-cell interference caused by the relatively high second transmit power 232. Such scheduling may include control signaling implemented via the core network between the enbs 112-1, 112-2. Such scheduling may include implementing a common time reference for the enbs 112-1, 112-2; thus, time synchronization between the eNBs 112-1, 112-2 may be achieved.

In a first example, such scheduling may involve co-scheduling of pilot signals transmitted by eNB112-1 (such as UL pilot signals transmitted by terminal 130-1 and received by eNB 112-1) with signals transmitted by eNB 112-2; that is, the pilot signals transmitted by the eNB112-1 may be scheduled in resources shared between the eNB112-1 and the eNB 112-2. In a second example, such scheduling may involve orthogonal scheduling of pilot signals transmitted by eNB112-1 (such as UL pilot signals transmitted by terminal 130-1 and received by eNB 112-1) with signals transmitted by eNB 112-2; that is, the pilot signals transmitted by the eNB112-1 may be scheduled in resources 305 dedicated to the eNB112-1 and not shared with the eNB 112-2. Orthogonality may be achieved by at least one of: FDMA, TDMA, and CDMA. For example, orthogonal resources 305 may be selectively used depending on the location of terminal 130-1. For example, the transmission intervals 302 of the second subset 322 may be selectively scheduled in the resources 305 shared between the eNB112-1 and the eNB112-2 according to the location of the terminal 130-1 transmitting the pilot signal. In one example, orthogonal scheduling may be preferred where terminal 130-1 is located near the edge of a cell bordering eNB112-2 (dashed area in fig. 17). In such an example, strong inter-cell interference is avoided because orthogonal resources are employed near the edge of cell 112-1A; on the other hand, if terminal 130-1 is located away from the edge of cell 112-1A (i.e., outside the dashed area in fig. 17), spectral efficiency is achieved by using shared resources.

Fig. 18 illustrates aspects relating to additional handover scenarios. In the example of fig. 18, the microcell 112-2A is implemented by the eNB 112-2. Sometimes, a microcell is called a pico (pico) cell. The macro cell 112-1A is implemented by the eNB 112-1. The terminal 130-1 attaches to the cellular network 100 via the eNB 112-2. Because the terminal 130-1 is in communication with the eNB112-2 implementing the microcell 112-2A, the magnitude of the first transmit power 231 is relatively small, as can be seen from the small range 130-1A. This is done in order to avoid interference with the pilot signal transmitted by the eNB 112-1. The magnitude of the second transmit power 232 is significantly larger, as can be seen from the range 130-1B. In particular, the larger second transmit power 232 facilitates the eNB112-1 to receive the UL pilot signal transmitted by the terminal 130-1. Based on the received UL pilot signal, the eNB112-1 can draw conclusions about the channel state between the terminal 130-1 and the eNB 112-2. In particular, backhaul signaling (backhaul signaling) between the eNBs 112-1, 112-2 may be reduced. This reduction in backhaul signaling may be particularly significant (legacy) where unlicensed frequency bands are used for communication between terminal 130-1 and eNB 112-2.

Fig. 19 illustrates aspects relating to additional handover scenarios. In the example of FIG. 19, the micro cells 112-2A, 112-3A are implemented by eNBs 112-2, 112-3, respectively. The macro cell 112-1A is implemented by the eNB 112-1. The terminal 130-1 attaches to the cellular network 100 via the eNB 112-1. When the terminal 130-1 approaches one of the microcells 112-2A, 112-3A, such approach may be detected in advance by the respective eNB112-2, 112-3 directly by means of the pilot signal transmitted at the higher second transmission power 232, see the corresponding range 130-1B. Specifically, because the pilot signals transmitted at the second transmit power 232 may be received by both eNBs 112-2, 112-3, the most appropriate microcells 112-2A, 112-3A may be selected. Backhaul signaling between the eNB112-1 and the eNBs 112-2, 112-3 is reduced or avoided.

Fig. 20 illustrates aspects related to transmitting pilot signals with a first transmit power 231 in the first subset 321 and pilot signals with a second transmit power 232 in the second subset 322. FIG. 20 is a signaling diagram of signaling between eNB112 and terminal 130-1. In the example of fig. 20, decision logic regarding enabling transmission of a pilot signal having a second transmit power 232 resides at the eNB 112. Specifically, at 1001, the eNB112 determines to realize the transmission of the pilot signal having the second transmission power 232.

Fig. 20 also illustrates aspects related to scheduling the transmission interval 302 of the second subset 322 between the eNB112 and the terminal 130-1. At 1001, the timing 322A of the transmission interval 302 of the second subset 322 is determined. In the example of fig. 20, the timing 322A corresponds to the transmission interval 302 during which the second subset 322 is reproduced (e.g., at a given period). Non-periodically recurring transmission intervals 302 are possible.

Next, a control message 1002 indicating the second transmission power 232, and optionally the first transmission power 231, is transmitted from the eNB112 to the terminal 130-1. For example, the control message 1002 may be an RRC control message. The control message 1002 also indicates the timing 322A. The transmission intervals 302 of the second subset 322 are continuously scheduled based on the control message 1002, e.g., until a new control message 1002 is transmitted from the eNB112 to the terminal 130-1.

Terminal 130-1 then transmits UL pilot signal 1003-. The second subset 322 is interleaved into the first subset 321; in detail, the pilot signal 1004 having the second transmission power 232 is transmitted between the pilot signals 1003, 1005 having the first transmission power 231. However, such time-domain interleaving is only an option. In other examples, other ways of distinguishing the first subset 321 from the second subset 322 may be chosen; for example, the first subset 321 and the second subset 322 may be distinguished from each other with respect to at least one of: in the frequency domain, in the spatial domain, in the code domain, etc.

Fig. 21 illustrates aspects related to transmitting pilot signals with a first transmit power 231 in the first subset 321 and pilot signals with a second transmit power 232 in the second subset 322. The example of fig. 21 generally corresponds to the example of fig. 20. In the example of fig. 21, the transmission intervals 302 of the second subset 322 are scheduled sporadically. Specifically, at 1001, the timing 322A is determined. Additionally, in the example of fig. 20, the timing 322A corresponds to reoccurring (e.g., at a given period) the transmission interval 302 of the second subset 322. However, in the scenario of fig. 21, dedicated control messages 1014, 1017 are transmitted from the eNB112 to the terminal 130-1, each of the dedicated control messages 1014, 1017 triggering transmission of a single UL pilot signal 1015, 1018. Therefore, the transmission intervals 302 of the second subset 322 are scheduled sporadically. It is not required to inform the terminal 130-1 about the timing 322A because each control message 1014, 1017 individually triggers the transmission of a respective UL pilot signal 1015, 1018 with the second transmit power 232.

In the case of fig. 20 and 21, the decision logic for deciding to use the higher second transmit power 232 resides at the eNB 112. Likewise, a second transmit power 232 is determined at the eNB 112. The eNB112 is also informed of the timing 322A with which to schedule the transmission interval 302 of the second subset 322. Accordingly, the eNB112 may perform accurate channel sensing based on well-defined parameters of the UL pilot signals transmitted at the second transmit power 232 in the second subset 322.

In some cases, it may also be possible for the decision logic for deciding to use the higher second transmit power 232 to reside at least partially at the terminal 130-1. Here, the terminal 130-1 may determine the timing 322A and/or the second transmit power 232 of the transmission interval 302 of the second subset 322. This situation may be applicable in case of limited control signaling (e.g. due to use of unlicensed bands and/or different involved operators). Here, bottom-up scheduling performed autonomously by respective terminals or other nodes may be relevant.

Fig. 22 illustrates aspects relating to transmitting pilot signals 1021, 1024 and 1026 with first transmit power 231 in the first subset 321 and transmitting pilot signals 1023 with second transmit power 232 in the second subset 322. In the example of fig. 22, decision logic for deciding to use the higher second transmit power 232 resides at terminal 130-1.

In the example of fig. 22, terminal 130-1 transmits UL pilot signals 1021, 1024 and 1026 in first subset 321 and at a first transmit power; terminal 130-1 transmits UL pilot signal 1023 at a second, higher transmit power 232. UL pilot signal 1023 indicates second transmit power 232 so that eNB112 is notified accordingly. A second transmit power 232 is determined at the terminal 130-1. To enable accurate channel sensing at the eNB112, the eNB112 should be informed about the second transmit power 232.

Different scenarios for implementing the pilot signal 1023 to indicate the second transmission power 232 are conceivable. For example, pilot signal 1023 may indicate second transmit power 232 explicitly or implicitly. For example, the pilot signal 1021, 1023, 1026 sequences can be associated with the same sequence generator. Thus, the same sequence generator can be used to generate the pilot signals 1021, 1023, 1026. In the example, the respective transmit power of each pilot signal 1021, 1023, 1026 is the input to the generator code. Specifically, for a given pilot signal 1021, 1023, 1026, there may be a unique mapping between the symbols output by the sequence generator and the transmit power input to the sequence generator. Thus, based on the particular symbols of a given pilot signal 1021, 1023, 1026, a conclusion can be drawn as to the respective transmit power 231, 232; as such, pilot signal 1023 implicitly indicates second transmit power 232. This reduces control signaling overhead.

In other cases, an explicit flag may be appended to pilot signal 1023; the flag may indicate the second transmit power 232, e.g., according to a predefined rule, etc. Thus, the pilot signal 1023 explicitly indicates the second transmission power 232.

With this technique, it is also possible for another terminal receiving the power-boosted pilot signal 1023 (see fig. 7, 8A, 8B, 9A, 9B, 10A, 10B, 11A and 11B) to know the second transmission power 232. The corresponding UL report message 902 may include an indicator indicating the second transmit power 232.

Fig. 23 illustrates aspects related to transmitting pilot signals 10131, 11035 and 1037 having a first transmit power 231 in the first subset 321 and transmitting pilot signals 1033 having a second transmit power 232 in the second subset 322. The example of fig. 23 generally corresponds to the example of fig. 22. 1031 corresponds to 1021. 1032 corresponds to 1022. 1033 corresponds to 1023. 1035 corresponds to 1024. 1036 corresponds to 1025. 1037 corresponds to 1026.

Decision logic for deciding to utilize the higher second transmit power 232 resides at the terminal 130-1. In the example of fig. 23, instead of implementing a pilot signal 1033 having a second transmit power 232 to indicate the second transmit power 232, a dedicated control message 1034 is communicated from the terminal 130-1 to the eNB 112. For example, control message 1034 may be an RRC control message or the like. Control message 1034 may be transmitted in a temporal context with pilot signal 1033, e.g., at the same transmission interval 302, etc. Control message 1034 may include an indicator indicating UL pilot signal 1033.

Further terminals receiving the power-boosted pilot signal 1023 (see fig. 7, 8A, 8B, 9A, 9B, 10A, 10B, 11A and 11B) may also learn the second transmit power 232 if a control message 1034 is broadcast to other devices. The corresponding UL report message 902 may include an indicator indicating the second transmit power 232.

Fig. 24 illustrates aspects related to a handover scenario. FIG. 24 is a signaling diagram of communications between eNB112-1, eNB112-2 and terminal 130-1. The aspect discussed with reference to fig. 24 may be employed, for example, in the context of fig. 17-19.

During a handoff, it is easier for the eNB112-2 to know the terminal 130-1 that is close to the coverage area if the terminal 130-1 employs a pilot signal with increased power. For example, in the case where the eNB112-2 receives only the pilot signal with increased power, a handover may be avoided because the coverage area has not been reached. Handover may also be prepared if terminal 130-1 is determined to be close to the coverage area based on the increased power pilot signal.

In the example of fig. 24, terminal 130-1 transmits UL pilot signal 1041 at first transmit power 231. The pilot signal 1041 is received by the eNB112-1 to which the terminal 130-1 is connected, and the terminal 130-1 attaches to the cellular network 100 via the eNB 112-1. The eNB112-2 does not receive the pilot signal 1041. This is due to the limited first transmit power 231.

The terminal 130-1 then transmits a pilot signal 1042 at the second transmit power 232. Both eNB112-1 and eNB112-2 receive pilot signal 1042. This is due to the increased second transmit power 232.

Based on the received pilot signal 1042, a handoff can be initiated. In the particular example of FIG. 24, the handover is initiated by the target eNB112-2 by communicating a handover request 1042 from the target eNB112-2 to the source eNB 112-1. In other examples, the handover may also be initiated by the source eNB 112-1. Additional handover procedures may be implemented in accordance with 3GPP TS 23.401 and 3GPP TS 36.300.

Fig. 25 illustrates aspects related to scheduling the transmission interval 302 of the second subset 322 between enbs 112-1, 112-2. FIG. 25 is a signaling diagram of communications between eNB112-1, eNB112-2 and terminal 130-1. The aspect discussed with reference to fig. 25 may be employed, for example, in the context of fig. 17-19.

At least one control message 1051 is communicated between the eNBs 112-1, 112-2. The at least one control message may indicate a timing 322A of the transmission intervals 302 of the second subset 322. The timing 322A may enable mitigation of inter-cell interference between the cell 112-1A associated with the eNB112-1 and the cell 112-2A associated with the eNB 112-2.

Next, a control message is transmitted from the eNB112-1 to the terminal 130-1. Control message 1052 indicates timing 322A. Optionally, the control message indicates the second transmit power 232 and/or the first transmit power 231. Terminal 130-1 may then transmit UL pilot signals 1053, 1054 according to timing 322A and optionally according to the specified first and second transmit powers 231, 232.

Fig. 26 schematically illustrates a terminal 130 that may be employed in various examples described herein. The terminal 130 includes: a processor 1301, a memory 1302 (e.g., a non-volatile memory), and an interface 1303. Interface 1303 is configured to communicate over wireless link 101. For example, interface 1303 may include an antenna array to employ MIMO or MAMI techniques. The processor 1301 is configured to obtain control data from the memory 1302. Execution of the control data causes processor 1302 to perform techniques as described herein, e.g., involving: receiving a UL pilot signal transmitted by the further terminal; scheduling a transmission interval to receive a subset of the UL pilot signals; determining a characteristic of the received UL pilot signal; transmitting a UL report message indicating characteristics of the received UL pilot signal; transmitting a pilot signal having a time-varying transmit power; transmitting a pilot signal indicating a transmission power; transmitting a control message indicating a transmission power of a pilot signal; scheduling a transmission interval of a pilot signal transmitting a specific transmission power; and/or determining a resource mapping and/or a transmission power of the pilot signal; and the like.

Fig. 27 schematically illustrates an eNB112 that may be employed in various examples described herein. The eNB112 includes: a processor 1121, a memory 1122 (e.g., a non-volatile memory), and an interface 1123. Interface 1123 is configured to communicate over wireless link 101. For example, interface 1123 may include an antenna array to employ MIMO or MAMI technology. The processor 1121 is configured to obtain control data from the memory 1122. Execution of the control data causes the processor 1121 to perform the techniques as described herein, for example, involving: receiving a UL pilot signal; scheduling a transmission interval for a subset of terminals to receive the UL pilot signals; determining a characteristic of the received UL pilot signal; determining characteristics of the received plurality of UL pilot signals; transmitting a UL report message indicating characteristics of the received UL pilot signal; transmitting a pilot signal having a time-varying transmit power; transmitting a pilot signal indicating a transmission power; transmitting a control message indicating a transmission power of a pilot signal; scheduling a transmission interval of a pilot signal transmitting a specific transmission power; performing link adaptation; performing channel sensing; and/or determining a resource mapping and/or a transmission power of a pilot signal; and the like.

Fig. 28 is a flow diagram of a method according to various embodiments. For example, the method according to fig. 28 may be performed by a terminal according to fig. 26.

At 2001, the first terminal 130, 130-1-130-4 receives at least one UL pilot signal 310-. For example, 2001 may be performed during the silence period 307, where the first terminals 130, 130-1-130-4 do not transmit the pilot signal 310-318 during the silence period 307. For example, 2001 may be performed continuously or intermittently by the first terminal 130, 130-1-130-4. For example, 2001 may be triggered by some event. For example, 2001 may be triggered by the respective transmission interval 302 that has been identified by the schedule; the scheduling may be between the eNBs 112, 112-1-112-3 and the first terminals 130, 130-1-130-4.

For example, UL pilot signal 310-310 received at 2001 may be selected from the group consisting of: demodulation Reference Signal (DRS) according to 3GPP TS36.211v13.0.0(2015-12) section 5.5.2; and Sounding Reference Signals (SRS) according to 3GPP TS36.211V13.0.0(2015-12) section 5.5.3.

At 2002, the first terminal 130, 130-1-130-4 sends a UL report message 902. The UL report message 902 indicates the characteristics of the received at least one UL pilot signal 310 and 318.

The characteristic may be indicative of information directly related to channel sensing, including, for example: the phase of received UL pilot signal 310-318; the amplitude of the received UL pilot signal 310-318; time offset of received UL pilot signal 310-318; and the like. Alternatively or additionally, the characteristic may indicate information that enables the eNB112, 112-1-112-3 receiving the UL report message 902 to draw conclusions about the originator of the UL pilot signal 310 and 318 (i.e., conclusions about the identity of the second terminal 130, 130-1-130-4). Such characteristics may be selected from the group comprising: the identity of the second terminal 130, 130-1-130-4; resource 305 of the at least one UL pilot signal 310-318; and resource identification information of the received at least one UL pilot signal 310-318. For example, based on the resources 305 of the at least one UL pilot signal 310-.

If multiple UL pilot signals 310-318 are received 2001, information regarding the multiple UL pilot signals 310-318 may be aggregated into the UL report message 902 sent 2002.

Fig. 29 is a flow diagram of a method according to various embodiments. For example, the method according to fig. 29 may be performed by the eNB112 according to fig. 27. At 2011, the eNB112, 112-1-112-3 receives the UL report message 902 from the first terminal 130, 130-1-130-4. The UL report message 902 indicates characteristics of at least one UL pilot signal 310 and 318 that have been received by the first terminal 130, 130-1-130-4. The Ul pilot signals 310-318 have been transmitted by the second terminals 130, 130-1-130-2. The eNB112 may also receive at least one UL pilot signal 310 and 318 reported by the UL report message 902.

Fig. 30 is a flow diagram of a method according to various embodiments. For example, the method according to fig. 30 may be performed by the terminal 130 according to fig. 26 and/or by the eNB112 according to fig. 27. At 2021, the pilot signal 310 with the first transmit power 231 is transmitted and/or received (transmitted) 318. Pilot signals with a first transmit power 231 are included in the first subset 321 of the transmission intervals 302.

At 2022, the pilot signal 310 with the second transmit power 232 is transmitted and/or received (transmitted) 318. The pilot signal with the second transmit power 232 is included in the second subset 322 of the transmission interval 303. The first subset 321 and the second subset 322 are interleaved in the time domain. However, such time-domain interleaving is only an option. In other examples, other ways of distinguishing the first subset 321 from the second subset 322 may be chosen; for example, the first subset 321 and the second subset 322 may be distinguished from each other with respect to at least one of: in the frequency domain, in the spatial domain, in the code domain, etc.

In the example of fig. 30, various types of pilot signals 310 and 318 may be employed for 2021 and 2022. In particular, a symbol (sign) type pilot signal may be employed for 2021 and 2022. One type of pilot signal may be characterized by a particular resource map 301 and/or a sequence generator for generating the corresponding sequence 310-318. Examples of pilot signal types include, but are not limited to, if the corresponding technology is used for the 3GPP LTE architecture: cell-specific reference signals (CRS) according to 3GPP TS36.211v13.0.0(2015-12) section 6.10.1; DL DRS according to 3GPP TS36.211v13.0.0(2015-12) section 6.10.3 a; CSI reference signals according to section 6.10.5 of 3GPP TS36.211v13.0.0 (2015-12); UL DRS according to 3GPP TS36.211v13.0.0(2015-12) section 5.5.2; and SRS according to 3GPP TS36.211v13.0.0(2015-12) section 5.5.3.

Fig. 31 is a flow diagram of a method according to various embodiments. For example, the method according to fig. 31 may be employed in combination with the method according to fig. 30.

At 2041, a factor between the size of the first subset 321 and the size of the second subset 322 is determined. In some cases, it may be desirable to transmit a greater number of pilot signals 310 at a lower first transmit power 231 than the number of pilot signals transmitted at a greater second transmit power 232; here, the factor may correspond to 2, 10, 100 or 1000, for example. Larger factors generally correspond to smaller interference.

At 2042, it is determined that the second transmit power 232 is greater than the factor of the first transmit power 231. In some cases, it may be desirable to achieve a significant factor, e.g., up to 1dB, 2dB, 3dB, or even greater. Thus, even if there is significant path loss (e.g., at a remote location), a pilot signal having the second transmit power 232 may be received; the corresponding range is increased. At the same time, increased interference may result.

At 2041 and 2042, various decision criteria may be considered in determining the respective factors. Example decision criteria include, but are not limited to: mobility; at least partially random processes; optimizing; the location of the terminal that sent and/or received (transmitted) the pilot signal; switching of the terminal; and the like.

For example, if the location of the terminal is associated with increased inter-cell interference (as may be the case if the terminal is located close to the cell edge), a larger factor between the size of the first subset 321 and the size of the second subset 322 may be determined at 2041 and/or a smaller factor between the second transmission power 232 and the first transmission power 231 may be determined at 2042. Thereby, interference is mitigated.

For example, if a handover of the terminal is imminent, it may be determined that the factor between the size of the first subset 321 and the size of the second subset 322 is closer to 1. Thereby facilitating accurate channel sensing. Handover can be accurately triggered.

At 2042, a control message is transmitted between the respective eNB112, 112-1-112-3 and the respective terminal 130, 130-1-130-4, the control message indicating the factor determined at 2041, 2042. For example, the control message may implicitly indicate a factor between the size of the first subset 321 and the size of the second subset 322, as determined at 2041, by scheduling the timing 322A of the transmission interval 302 of the second subset 322.

In summary, the above has described a technique capable of efficiently transmitting pilot signals such as UL pilot signals or DL pilot signals or sidelink pilot signals.

In particular, techniques have been described that enable a first terminal to receive a UL pilot signal transmitted by at least one second terminal. Thereby, additional information about the radio link status may be collected.

In addition, techniques have been described that can temporarily increase the transmit power of a given type of pilot signal. In detail, techniques have been described that are capable of transmitting pilot signals at (i) a first transmit power in a first subset of a sequence of transmission intervals and (ii) a second, higher transmit power in a second subset of the sequence of transmission intervals, according to a given repetition resource mapping. These pilot signal sequences across the first subset and the second subset may be associated with the same sequence generator. By temporarily increasing the transmission power, a pilot signal of increased power can be received for the additional entity; thereby, additional information about the status of the radio link can be collected.

Such techniques may be used for various use cases. Fig. 32 is a flow diagram of a method according to various embodiments. Fig. 32 illustrates aspects of various use cases regarding such additional information that depends on the state of the radio link.

At 2051, one or more characteristics of the received at least one pilot signal 310 and 318 are determined. These characteristics may include, but are not limited to: an amplitude of the received at least one pilot signal 310-318; the phase of the received at least one pilot signal 310-318; resource 305 of the received at least one pilot signal 310-318; a time offset of the received at least one pilot signal 310-318; and the angle of arrival of the received at least one pilot signal 310-318.

These one or more characteristics may be used in accordance with one or more use cases in accordance with 2052-2057. The various use cases according to 2052-2057 may be employed individually or in combination with one another.

The first example corresponds to 2052. At 2052, the location of the first terminal 130, 130-1-130-4 that received the UL pilot signal 310 and 318 transmitted by the second terminal 130, 130-1-130-4 is determined. Alternatively or in addition, at 2052, the location of the second terminal 130, 130-1-130-4 that sent the UL pilot signal 310-. For example, the relative position of the first terminal 130, 130-1-130-4 with respect to the second terminal 130, 130-1-130-4 may be determined. For example, the relative positions may be defined with respect to one or more eNBs 112, 112-1-112-3. For example, as part of 2052, the travel time of the UL pilot signal 310 and 318 from the second terminal 130, 130-1-130-4 to the first terminal 130, 130-1-130-4 may be considered. Alternatively or additionally, the angle of arrival may be considered. Triangulation techniques may be employed. Alternatively or additionally, the travel time of the UL pilot signal 310-130-4 from the second terminal 130, 130-1-130-4 to the respective eNB112, 112-1-112-3 may be considered. Alternatively or additionally, the travel time of the additional UL pilot signals 310-130-4 from the first terminals 130, 130-1-130-4 to the respective eNBs 112, 112-1-112-3 may be considered. The positioning based on the UL pilot signals 310-318 may be supplemented by further positioning techniques; in particular, in this context, it may be advantageous if it is known that the identities of all participating terminals 130, 130-1-130-4 accurately fuse the positioning information. Further localization techniques may include: GPS, compass, gyroscope, pressure sensor; and the like. Thus, as can be seen from 2052, the increased power pilot signal 310-318 can be used as a positioning beacon.

Thus, as part of 2052, a terminal 130, 130-1-130-4 receiving/detecting a set 318 of UL pilot signals 310 and 130-1-130-4 originating from other terminals 130, 130-1-130-4 may use such information to perform locally the calculation of position information/location of the other terminals 130, 130-1-130-4 relative to itself. In case the first terminal 130, 130-1-130-4 receiving the UL pilot signal has information about its own location available, e.g. by means of a Global Positioning System (GPS) or the like, the first terminal 130, 130-1-130-4 may enable an initial location estimation of the second terminal 130, 130-1-130-4. To detect the angle of arrival from the UL pilot signals 310-318, multi-antenna reception by MIMO or MAMI techniques may be employed. The additional angle information may supplement this information, for example by using a compass or another sensor. In further examples, these additional data may also be reported by the first terminal 130, 130-1-130-4 to the eNB112, 112-1-112-3 as part of the UL report message 902. The UL report message 902 may be sent at a specific request or may be triggered actively/autonomously. With this technique, it is possible that the received UL pilot signals 310-318 may be combined with additional terminal specific information (such as location, detected angle of arrival, mobility information, compass information, pressure sensor information, etc.); all this information can be used by the network to further combine with the available information to improve positioning accuracy. For example, the network may combine several different UL report messages for terminals 130, 130-1-130-4 to further refine the position estimate. The UL report message 902 may contain an indicator indicating the geographical location, e.g., from GPS, and relative location information from the plurality of terminals 130, 130-1-130-4. Thereby, the network obtains the geographical/absolute position of the target terminal 130, 130-1-130-4 in an accurate manner.

The second use case corresponds to 2053. At 2053, a relay channel is established. For example, the relay channel may be between the first terminal 130, 130-1-130-4 receiving the UL pilot signal 310 and 318 transmitted by the second terminal 130, 130-1-130-4 and the corresponding eNB112, 112-1-112-3. For example, the relay channel may employ the second terminals 130, 130-1-130-4 as relays. For example, if the first terminal 130, 130-1-130-4 receives the UL pilot signal 310 and 318 transmitted by the second terminal 130, 130-1-130-4, and determines that the path loss between the second terminal 130, 130-1-130-4 and the first terminal 130, 130-1-130-4 is relatively small based on the received UL pilot signal 310 and 318, then it may be determined that the establishment of the relay channel is advantageous, e.g., in terms of transmission reliability and/or energy consumption.

As an example, at 2053, information obtained from the received UL pilot signals 310-318 may be used to select the appropriate terminal 130, 130-1-130-4 for the relay function. For example, a new relay may be selected from a plurality of candidate relays. For example, the selection of relays may be based on certain device types, such as a particular class of terminals 130, 130-1-130-4 defined within the cellular network 100 that is capable of relaying or acting as an information forwarding link between the additional terminals 130, 130-1-130-4 and the enbs 112, 112-1-112-3. To understand which terminals 130, 130-1-130-4 are in proximity to each other and thereby select a suitable device for relaying, the concept of a first terminal 130, 130-1-130-4 receiving an UL pilot signal 310 and 318 transmitted by at least one second terminal 130, 130-1-130-4 as described herein may be employed. In particular, as described above, the positioning information derived from 2052 may also be considered as part of 2053.

The third example corresponds to 2054. At 2054, a sidelink channel is established. For example, the sidelink channel may be between receiving the UL pilot signal 310 and 318 transmitted by the second terminal 130, 130-1-130-4 to heat the first terminal 130, 130-1-130-4. For example, if the first terminal 130, 130-1-130-4 receives the UL pilot signal 310 transmitted by the second terminal 130, 130-1-130-4 and determines that the path loss between the second terminal 130, 130-1-130-4 and the first terminal 130, 130-1-130-4 is relatively small, then it may be determined that it may be advantageous to establish the sidelink channel, e.g., in terms of transmission reliability and/or energy consumption and/or resource allocation and/or delay. Thus, the power boosted pilot signal 310-318 may be used as the D2D discovery signal.

The fourth usage corresponds to 2055. At 2055, a repetition resource mapping for transmitting the pilot signal 310-318 is determined. For example, the resource map 301, 301A may be determined to be repeated such that the resource 305 is shared between the two terminals 130, 130-1-130-4 transmitting the pilot signal 310-318. For example, the resource mapping 301, 301A may be determined to be repeated such that the resource 305 is not shared between the two terminals 130, 130-1-130-4 transmitting the pilot signal 310-318; FDMA, TDMA and/or CDMA, etc. may be employed. For example, at 2055, the position of the two terminals 130, 130-1-130-4 relative to each other may be considered; to this end, the techniques described above with reference to 2052 and/or further positioning techniques may be relied upon.

As an example, as part of 2055, if there is no UL report message 902 received by the eNBs 112, 112-1-112-3, the UL report message 902 indicates activity of the UL pilot signal 310 plus 318 in a resource that may be available for transmission of the pilot signal 310 plus 318. Inter-cell interference is not expected in such resources.

In a further example, as part of 2055, if the eNB112, 112-1-112-3 knows the location of the participating terminal 130, 130-1-130-4, resources can be used to transmit the pilot signal 310 and 318 in different parts of the cell where no or only little interference is desired. Thus, pilot pollution can be avoided; while at the same time, resources are efficiently utilized.

The fifth usage corresponds to 2056. 2056 corresponds to channel sensing. At 2056, the status of one or more channels 261- "263 implemented over the radio link 101 is determined. By considering the pilot signal 310 with increased power 318, more data points may be considered in determining the channel state. Thus, highly accurate channel sensing may be employed. In particular, channel sensing may be used for MIMO channels. In general, operation of communications over a MIMO channel requires highly accurate channel sensing. Such highly accurate channel sensing may be achieved by considering more data points as described above. This technique may find particular application for MAMI scenarios. For example, MIMO and/or MAMI channel sensing may rely on reciprocity between UL and DL states. Generally, the MAMI case relies only on the UL pilot signal 310-318. In some examples, Frequency Division Duplex (FDD) channels may be considered. Here, due to the smaller bandwidth availability/consistency, separate UL and DL pilot signals 310 and 318 may be transmitted. In a channel with a large bandwidth, the multiple pilot signals 310-318 may be transmitted at different frequencies to detect different subbands.

The sixth use case corresponds to 2057. At 2057, a handover is prepared. For example, a handover may be made between two neighboring cells. Handover may also be performed between a macrocell and a microcell. The advance notice of the terminals 130, 130-1-130-4 near the cell edge can be established by using the pilot signal with increased power 310-318. Thus, the exact triggering criteria for performing the handover may be considered.

Although the invention has been shown and described with respect to certain preferred embodiments, equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications, and is limited only by the scope of the following claims.

For example, while the various examples above have been described with reference to UL pilot signals, the respective techniques can be readily implemented with reference to DL pilot signals or sidelink pilot signals.

For example, while the various examples above have been described with reference to E-UTRAN, other RATs may be employed.

For example, while various examples above have been described with reference to a report message indicating at least one characteristic of received at least one uplink pilot signal, similar techniques may be readily implemented for a report message indicating at least one characteristic of received at least one downlink pilot signal.

For example, although reference has been made above to duplicate resource mappings, in other examples, non-duplicate resource mappings may also be employed.

Claims (20)

1. A method performed by a device (112, 112-1-112-3, 130-1-130-4), the method comprising the steps of:

-in a first subset (321, 322) of a sequence of transmission intervals (302): transmitting a pilot signal (310) with a non-zero first transmission power (231, 232) according to a resource mapping (301, 301A) over a radio link (101) of a cellular network (100),

-in a second subset (321, 322) of the sequence of transmission intervals (302): transmitting a pilot signal (310) having a non-zero second transmission power (231, 232) being larger than the first transmission power (231, 232) over the radio link (101) according to the resource mapping (301, 301A),

-receive a control message from a network node of the cellular network (100), the control message indicating a persistent scheduling of the transmission intervals of the second subset,

wherein the first subset and the second subset are interleaved in the time domain, wherein the transmission intervals of the second subset recur with a given periodicity indicated by the control message.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

wherein the pilot signal (310) transmitted in the second subset (321, 322) indicates the second transmit power (231, 232).

3. The method according to claim 1 or 2, further comprising the steps of:

-transmitting at least one control message (1002, 1014, 1017, 1052) indicating the second transmission power (231, 232) between an access node (112, 112-1-112-3) and a terminal (130, 130-1-130-4) of the cellular network (100) over the radio link (101).

4. The method according to claim 1 or 2, further comprising the steps of:

-scheduling (1002, 1014, 1017) the transmission intervals (302) of the second subset (321, 322) sporadically or persistently between a terminal (130, 130-1-130-4) and an access node (112, 112-1-112-3) of the cellular network (100).

5. The method according to claim 1 or 2, further comprising the steps of:

-scheduling (1051) the transmission intervals (302) of the second subset (321, 322) between an access node (112, 112-1-112-3) of the cellular network (100) and a further access node (112, 112-1-112-3) of the cellular network (100).

6. The method of claim 5, wherein the first and second light sources are selected from the group consisting of,

wherein the transmission intervals (302) of the second subset (321, 322) are selectively scheduled in resources (305) shared between the access node (112, 112-1-112-3) and the further access node (112, 112-1-112-3) depending on the location of the terminal (130, 130-1-130-4) transmitting the pilot signal (310-318).

7. The method according to claim 1 or 2,

wherein the pilot signal (310) -318 sequence transmitted in the first subset (321, 322) and the pilot signal (310) -318 sequence transmitted in the second subset (321, 322) are associated with the same sequence generator.

8. The method of claim 7, wherein the first and second light sources are selected from the group consisting of,

wherein each transmit power (231, 232) is an input to the sequence generator.

9. The method according to claim 1 or 2,

wherein the size of the first subset (321, 322) is at least 2 times the size of the second subset (321, 322).

10. The method according to claim 1 or 2,

wherein the resource mapping (301, 301A) is repetitive.

11. The method according to claim 1 or 2, further comprising the steps of:

-determining at least one of a factor between the size of the first subset (321, 322) and the size of the second subset (321, 322) and a factor (233) between the second transmission power (231, 232) and the first transmission power (231, 232) based on at least a partially random and/or optimized process.

12. The method according to claim 1 or 2, further comprising the steps of:

-determining at least one of a factor between the size of the first subset (321, 322) and the size of the second subset (321, 322) and a factor (233) between the second transmission power (231, 232) and the first transmission power (231, 232) based on the location of the terminal (130, 130-1-130-4) transmitting the pilot signal (310-318).

13. The method according to claim 1 or 2, further comprising the steps of:

-determining at least one of a factor between the size of the first subset (321, 322) and the size of the second subset (321, 322) and a factor (233) between the second transmission power (231, 232) and the first transmission power (231, 232) based on a handover of a terminal (130, 130-1-130-4) transmitting the pilot signal (310-318) from an access node (112, 112-1-112-3) of the cellular network (100) to a further access node (112, 112-1-112-3) of the cellular network (100).

14. The method according to claim 1 or 2,

wherein the pilot signal (310-318) is selected from the group consisting of: an uplink pilot signal (310-318); downlink pilot signals (310-318); a sidelink pilot signal (310-318); cell-specific pilot signals (310-318); relaying the pilot signal (310-318); and terminal specific pilot signals (310-318).

15. The method according to claim 1 or 2,

wherein the pilot signal (310-318) is an uplink pilot signal (310-318) transmitted by a terminal (130, 130-1-130-4) attached to the cellular network (100),

wherein the transmission of the pilot signal (310) in the second subset (321, 322) comprises the steps of: the access node (112, 112-1-112-3) of the cellular network (100) receives the pilot signal (310) and 318, and a further access node (112, 112-1-112-3) of the cellular network (100) receives the pilot signal (310).

16. The method of claim 15, further comprising the steps of:

-based on at least one characteristic of the pilot signal (310) received by the access node (112, 112-1-112-3) and the further access node (112, 112-1-112-3): determining a relative position of the terminal (130, 130-1-130-4) with respect to at least one of the access node (112, 112-1-112-3) and the further access node (112, 112-1-112-3).

17. The method according to claim 1 or 2, further comprising the steps of:

-based on at least one characteristic of the pilot signal (310- & 318) in the first subset (321, 322) and at least one characteristic of the pilot signal (310- & 318) in the second subset (321, 322): the state of a multiple-input multiple-output, MIMO, channel (261-263) implemented over the radio link (101) is determined.

18. The method according to claim 1 or 2,

wherein the first subset (321, 322) and the second subset (321, 322) differ from each other at least in part in at least one of: a time domain; a frequency domain; space domain and code domain.

19. A terminal device (112, 112-1-112-3, 130-1-130-4), the terminal device comprising:

an interface (1123, 1303) configured to transceive over a radio link (101) of a cellular network (100),

-at least one processor (1121, 1301) configured to transmit pilot signals (310) with non-zero first transmission power (231, 232) in a first subset (321, 322) of a sequence of transmission intervals (302) according to a resource mapping (301, 301A) over the radio link (101) of the cellular network (100),

wherein the at least one processor (1121, 1301) is further configured to transmit a pilot signal (310) with a non-zero second transmission power (231, 232) being larger than the first transmission power (231, 232) in a second subset (321, 322) of the sequence of transmission intervals (302) over the radio link (101) according to the resource mapping (301, 301A),

wherein the at least one processor (1121, 1301) is further configured to receive a control message from a network node of the cellular network (100), the control message indicating a persistent scheduling of the transmission intervals of the second subset,

wherein the first subset and the second subset are interleaved in the time domain, wherein the transmission intervals of the second subset recur with a given periodicity indicated by the control message.

20. Terminal device (112, 112-1-112-3, 130-1-130-4) according to claim 19,

wherein the terminal device performs the method of any one of claims 1-18.

Images